Deoxycholic acid promotes the growth of colonic aberrant crypt foci

AKR/J mice are resistant to the tumorigenic properties of the colon carcinogen, azoxymethane (AOM). Following AOM exposure, limited numbers of preneoplastic lesions, referred to as aberrant crypt foci (ACF), are formed in the colon, and their progression to tumors rarely occurs. To determine whether genetic resistance can be overcome by exposure to a dietary tumor promoter, AOM-exposed AKR/J mice were fed a diet containing 0.25% deoxycholic add (DCA). DCA exposure was begun 1 wk prior to or 1 wk after tumor initiation with AOM. Mice placed on the DCA diet prior to AOM treatment developed a significantly higher multiplicity of ACF compared to AOM-exposed mice fed a control diet (15.50 ± 0.96 vs. 6.17 ± 0.48, respectively; P < 0.05). When DCA exposure was begun after AOM treatment (post-initiation), ACF formation was further enhanced (34.00 ± 1.22). Interestingly, increased numbers of ACF were associated with the presence of nuclear β-catenin, assessed by immunohistochemistry. While ∼33% of ACF from mice exposed to DCA prior to AOM treatment contained positive nuclear β-catenin staining, ∼77% of ACF from mice fed DCA after AOM were positive. Accumulation of nuclear β-catenin was not associated with a loss of E-cadherin from the plasma membrane, although loss of APC staining was a consistent feature of most AOM-induced ACF, regardless of DCA exposure. These results demonstrate that exposure to DCA, an important digestive component, is sufficient to sensitize the resistant AKR/J colon to formation of high-grade dysplasia, and that nuclear translocation of β-catenin may play an important role in this process.